Most of southern Australia is facing increased mice populations heading into seeding but SA graingrowers are said to be on the front foot this season, with many already filling their sheds with substantial bait supplies.
CSIRO researcher Steve Henry, who had been surveying mouse activity for a GRDC-funded project, said mouse abundance had increased on SA’s Northern Adelaide Plains and Yorke Peninsula in particular.
Being well into the mice breeding season, Mr Henry expects populations could further rise in the lead-up to sowing, causing concern for growers who have not yet baited.
“Our routine mice monitoring project that we undertook produced results from March that were higher than normal across most of the southern cropping zone,” Mr Henry said.
“The Adelaide Plains did not have ultra high numbers but they were definitely not low, but in north western Vic at Walpeup, from 100 traps set over three nights at the beginning of March, we trapped between 70 and 80 mice per night.”
Rapid assessment counting of active burrows at 13 sites across the YP revealed extremities, with some sites at zero and others containing up to 300 active burrows a hectare, equating to about 600 mice.
“Numbers might be patchy but they are definitely higher than normal compared with this time last year,” Mr Henry said.
Patchy does not mean low numbers, Mr Henry says, and he encourages farmers to walk through paddocks and look for active burrows.
“If a grower is still four to six weeks away from sowing and they have a mice problem, it is worthwhile applying bait to try reduce the population but that window has almost closed, so straight off the back of the seeder is best practice,” Mr Henry said.
“But baiting now and leaving the gap before seeding means, if a mouse gets a sublethal dose, they forget about being sick and take the bait at seeding.
“We were talking about mice well before this time last year so in terms of potential for an outbreak, this year the difference is farmers are really switched on about mice and prepared with bait.”
Wilhelm Rural’s Brenton Wilhelm distributes Last Supper to SA’s five regional bait stations and said 2018 was the first year farmers were a step ahead of a possible mice problem.
“As a consequence of last year, most growers are storing a lot of bait on-farm,” he said.
Wilhelm Rural has already imported 30,000 kilograms of zinc phosphide to make 920 tonnes of mice bait, which is equal to the same amount used for the entire 2017 season.
Mr Wilhem said it is expected 60,000kg will be used in 2018, doubling the amount which has been brought into SA in the past.
“The bait will arrive this month and most of the end bait is already ordered,” he said.
“This time last year farmers would not have been stockpiling bait.”
Although supply requirements have increased, Mr Wilhelm believes it might not be a case of greater mice populations but rather a case of prepared farmers.
Spring baiting slows breeding
MALLALA graingrower Paul Lush is taking early action, and has begun injecting water into active burrows as a management tool after mice monitoring data revealed populations were active in his paddocks.
Out of 100 traps monitored by CSIRO researchers for three nights in March, 25 per cent of traps were activated and Mr Lush said he was surprised to see populations decline from last year’s 57pc.
“We have only caught three-quarter grown mice and no adults – we bait in spring and last year we were catching adult mice, so we seem to have interrupted the breeding cycle,” he said.
“In 2016 we had a wet finish and summer rain, and we had a big mice problem so I think summer rain seems to be driving the increase rather than a food source.
“The lentil paddock that was wind damaged had no mice and the canola paddock with no food was severe.”
Mr Lush also baits in early autumn and the first night after seeding.
“Our new batch of bait has just arrived – we were really organised this year,” he said.
